Tachycardia is a type of cardiac arrhythmia and is a serious, often-times, fatal condition characterized by rapid, uncontrolled, and ineffective beating of the heart. Most tachycardia is one of two broad categories: ventricular tachycardia (hereinafter VT) and supraventricular tachycardia (hereinafter SVT). VT occurs in the lower chambers of the heart, the ventricles, and frequently leads to serious complications, including sudden cardiac death. Atrial fibrillation and flutter, forms of SVT, originate in the upper chambers of the heart, the atria, and often result in chest pain, fatigue and dizziness and, while generally not life-threatening, is a leading cause of stroke in the United States.
Currently, many cases of VT and SVT are treated by drugs that modify the electrical characteristics of the heart tissue. However, the drugs do not eliminate or may not completely control the arrhythmia. In many cases of sustained VT, implantable cardiac defibrillators are used which deliver powerful shocks to the heart when fibrillation is detected. Concurrent treatment with drugs is standard therapy and each implantation of a cardiac defibrillator, of which there may be more than one per patient, is very expensive.
Some forms of SVT are treated by endocardial ablation, a minimally invasive procedure. During endocardial ablation, a mapping catheter is passed through an artery or vein into the patient's heart to find the site(s) of the arrhythmogenic tissue, the tissue from which the tachycardia originate. This same catheter or a separate catheter is used to transmit sufficient energy to thermally damage the tissue either by heating or cooling. (FIG. 1)
In atrial fibrillation the regular pumping action of the atria is replaced by a disorganized, ineffective quivering caused by chaotic conduction of electrical signals through the upper chambers of the heart. Although not immediately life threatening, atrial fibrillation may cause up to a 30% reduction in cardiac output and can lead to more serious conditions, including the formation of blood clots in the atria that can dislodge and travel to the brain resulting in stroke. Currently, the only curative treatment for atrial fibrillation is the surgical “maze procedure”, an open heart procedure in which the surgeon makes several incisions in the right and left atria creating scar tissue to electrically separate portions of the atria Despite clinical success of the maze procedure, it is time-consuming and demanding. The procedure requires open heart surgery and is very expensive. Accordingly, only a modest number of maze procedures are performed annually in a limited number of centers.
Another use of ablation technology, either endocardial or epicardial, is transmyocardial revascularization. The creation of small ablation holes results in genesis of new blood vessels, providing a source of blood flow in areas of the heart not receiving sufficient blood.
The present invention provides another apparatus and method for treating cardiac arrhythmia, that may be widely applicable. The present invention also provides an apparatus for transmyocardial revascularization.